1. Field of the Invention
The present invention relates to a capacitor capacitance diagnosis device which determines adequacy of capacitor capacitance, and to an electric power apparatus which includes the capacitor capacitance diagnosis device and has an electromagnetic operating mechanism that is operative when an electromagnetic coil is energized by energy accumulated in a capacitor.
2. Description of the Related Art
An electric power apparatus for use in an electrical feeder system is required to ensure reliability over a long period. Therefore, periodic diagnosis of the apparatus is indispensable. For example, in an encapsulated composite insulation switchgear, opening and closing operation of a vacuum circuit breaker is performed by an electromagnetic operating mechanism by means of an electromagnetic coil, and energy accumulated in a capacitor is used to open a contact. A large capacity electrolytic capacitor necessary for operating an electric power apparatus is regarded as a limited lifetime component; and therefore, degradation in capacitor capacitance due to aged deterioration is concerned. Consequently, in order to ensure reliability of a vacuum circuit breaker, the followings are required: the capacitor is periodically removed, capacitance is checked, capacitor capacitance diagnosis for determining adequacy of the capacitor is carried out, and replacement of the capacitor is carried out in the case where deterioration or the like is recognized. However, checking of the capacitor other than time of periodic inspection makes the electric power apparatus stop, and the number of diagnoses is limited. If a diagnosis device can determine adequacy of capacitor capacitance during operation of the electric power apparatus without detaching, the number of diagnosis frequencies can be considerably increased without stopping the apparatus and an improvement in reliability is expected.
In a known capacitor capacitance diagnosis circuit of a backup capacitor for use in an air bag of a passive safety device for vehicles, a discharge circuit composed of a resistor and a switching circuit connected in series are connected to a capacitor in parallel; the switching circuit of the discharge circuit is kept in an ON state for a certain time; a ratio between a charging voltage value V1 of the capacitor just before the ON state and a terminal voltage change value (V1-V2) of the capacitor due to discharge for the certain time is calculated; its calculation result is compared with a reference value; and accordingly, adequacy of capacitor capacitance is diagnosed. This actualizes assured and accurate diagnosis without being influenced by variation in output voltage of a DC power supply connected to the capacitor. Incidentally, the diagnosis of the capacitor is carried out at starting of a vehicle (for example, see Japanese Unexamined Patent Publication No. H9-229976).
In addition, in other known capacitor capacitance diagnosis device of a backup capacitor for use in an air bag of a passive safety device for vehicles, a voltage value across a capacitor is compared with a threshold to diagnose abnormality of the capacitor. The capacitor capacitance diagnosis device includes a detection unit which detects a threshold and a voltage value across the capacitor (initial value) in starting charging, and a unit which diagnoses abnormality of the capacitor by variably setting the threshold to not less than the initial value on the basis of the initial value and by comparing this variably set threshold with a voltage value across the capacitor after starting charging. This actualizes assured diagnosis of the abnormality of the capacitor even when an electric charge is already present at a time of starting charging. Incidentally, the diagnosis of the capacitor is carried out before running (for example, see Japanese Unexamined Patent Publication No. H6-207959).
However, in the known capacitor capacitance diagnosis circuit and capacitor abnormality diagnosis device, both have the objective of diagnosing the backup capacitor of the air bag for vehicles and the diagnosis is carried out only at starting of a vehicle just after inputting an ignition switch, and regular diagnosis during driving is not assumed. Once operation is started, the operation is used in the longer term; and therefore, there is a problem in that this application cannot be used for capacitor capacitance diagnosis for use in an electromagnetic operating mechanism of an electric power apparatus which needs periodic diagnosis of capacitor capacitance during the operation.